GC.ReRegisterForFinalize Method (Object)

 

Requests that the system call the finalizer for the specified object for which SuppressFinalize has previously been called.

Namespace:   System
Assembly:  mscorlib (in mscorlib.dll)

Public Shared Sub ReRegisterForFinalize (
	obj As Object
)

Parameters

obj
Type: System.Object

The object that a finalizer must be called for.

Exception Condition
ArgumentNullException

obj is null.

The ReRegisterForFinalize method adds the obj parameter to the list of objects that request finalization before the garbage collector frees the object. The obj parameter must be the caller of this method.

Calling the ReRegisterForFinalize method does not guarantee that the garbage collector will call an object's finalizer.

By default, all objects that implement finalizers are added to the list of objects that require finalization; however, an object might have already been finalized or might have disabled finalization by calling the SuppressFinalize method.

A finalizer can use this method to resurrect itself or an object that it references.

The following example demonstrates how to use the ReRegisterForFinalize method to finalize an object a second time after garbage collection.

Imports System

Namespace ReRegisterForFinalizeExample
    Class MyMainClass
        Shared Sub Main()
            'Create a MyFinalizeObject.
            Dim mfo As New MyFinalizeObject()

            'Release the reference to mfo.
            mfo = Nothing

            'Force a garbage collection.
            GC.Collect()

            'At this point mfo will have gone through the first Finalize.
            'There should now be a reference to mfo in the static
            'MyFinalizeObject.currentInstance field.  Setting this value
            'to null and forcing another garbage collection will now
            'cause the object to Finalize permanently.
            MyFinalizeObject.currentInstance = Nothing
            GC.Collect()
        End Sub
    End Class

    Class MyFinalizeObject
        Public Shared currentInstance As MyFinalizeObject = Nothing
        Private hasFinalized As Boolean = False

        Protected Overrides Sub Finalize()
            If hasFinalized = False Then
                Console.WriteLine("First finalization")

                'Put this object back into a root by creating
                'a reference to it.
                MyFinalizeObject.currentInstance = Me

                'Indicate that this instance has finalized once.
                hasFinalized = True

                'Place a reference to this object back in the
                'finalization queue.
                GC.ReRegisterForFinalize(Me)
            Else
                Console.WriteLine("Second finalization")
            End If
            MyBase.Finalize()
        End Sub
    End Class
End Namespace

Universal Windows Platform
Available since 8
.NET Framework
Available since 1.1
Portable Class Library
Supported in: portable .NET platforms
Silverlight
Available since 2.0
Windows Phone Silverlight
Available since 7.0
Windows Phone
Available since 8.1
Return to top
Show: